There have been a number of proposals for classifying vehicles and other similar terrestrial moving objects as relatively heavy or relatively light based on an analysis of the seismic vibration caused by the vehicle as it moves along the ground. Similarly, the acoustic signals generated by moving vehicles also have been used to determine certain gross characteristics, such as heavy vs. light. The following list of patents shows certain embodiments of these proposals. The differences between these proposals and applicant's invention will be discussed in a prior art statement, filed in conjunction with this application.